Glueless interlocks for folding box panels



April 1968 c. J. PlERcEyJR 3,380,645

GLUELESS INTERLOCKS FOR FOLDING BOX PANELS Filed May 5, 1967 INVENTOR.

J hesfer J Pierce, Jr,

2 Sheets-Sheet 1 April 30, 1968 c. J. PIERCE, JR 3,3

GLUELESS INTERLOCKS FOR FOLDING BOX PANELS Filed May 5, 1967 2 Sheets-Sheet 2 INVENTOR. Chesfer J. Pierce, Jr.

ATTORNEY United States Patent O 3,380,645 GLUELESS INTERLOCKS FOR FOLDING BOX PANELS Chester J. Pierce, Jr., Palo Alto, Calif., assignor to Certipak Corporation, New York, N.Y., a corporation of Delaware Filed May 5, 1967, Ser. No. 636,436 4 Claims. (Cl. 229-40) ABSTRACT OF THE DISCLOSURE The present improvements are of a glueless interlock between two panels of a folding box of the general lock type in which a tongue on one panel is inserted in a slot in the other panel and is prevented from being withdrawn by a locking tab. As improved, the slot is formed as an aperture and the locking tab is formed in the body proper of the one panel outside the confines of the tongue, and is accommodated, except for its engaging tip, in the space provided by the aperture in the other panel.

BACKGROUND OF THE INVENTION (1) Field of the invention-The present invention provides an improved glueless interlock for two panels of a folding box made from paperboard or other suitable foldable sheet material, and may be employed for connecting together panels of a folding box at a box corner and also for connecting together the ends of a sleeve-like box, of which open ended bottle or can carriers are examples.

(2) Description of the prior art.-It is known to interconnect folding box panels by means of a tongue on one panel, which tongue is inserted in a slot in the other panel supplemented by a locking tab on the tongue which prevents withdrawal of the tongue by engagement with an edge portion of the slot.

In order to form the engagement it is necessary to exert a force on the tab at some distance from its tip, the application of the force being in a direction normal to the plane of the tab. This force displaces the tip from a position overlying the other panel, past the edge, into a position underlying the other panel.

If, however, two panel thicknesses are present at the point where the force is exerted, the force is likely to cause displacement of the engagement edge away from the tip of the locking tab, thus making formation of the engagement difficult.

In such a case a relatively great movement of the lock- SUMMARY OF THE INVENTION One of the present improvements is the provision of an aperture in the second panel below the area without which the force is applied to the locking tab on the one pane The provision of an aperture leads to several advantages. Firstly, the second panel is not displaced. Secondly, space is provided into which the locking tab, except for its tip, is moved. Thirdly, the edges of the aperture may be utilized for curving or curling the body of the locking tab slightly by depression of its central portion in relation to its lateral portions. This may be accomplished by forming a central tab on one edge of the aperture pposite the engagement edge and by conveying the lateral edges of the aperture towards the engagement edge. The central tab bears down on the locking tab centrally and the lateral edges raise the lateral portions of the locking tab.

As a further improvement, the tab tip is located within the body of the panel in which the tongue is formed, rather than within the tongue, as was previous practice. In the improved construction a relatively large area of the locking tab remains accessible for application of the engaging force even if the tongue is fully inserted.

The various objects, features and advantages of this invention will appear more fully from the detailed description which follows accompanied by drawings showing, for the purpose of illustration, two embodiments of the invention. The invention also resides in certain new and original features of construction and combination of elements as hereinafter set forth and claimed.

Although the characteristic features of the invention which are believed to be novel will be particularly pointed out in the claims appended hereto, the invention itself, its objects and advantages and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a blank portion, the ends of Which are to be connected together;

FIG. 2 is a perspective view of the interlock partially engaged, portions being shown broken away;

FIG. 3 is a perspective view of the assembly of FIG. 2 after complete engagement;

FIGURE 4 is a modification of the form of interlock shown in FIGURE 1;

FIG. 5 is a plan view of a blank portion designed to be assembled as a box corner;

FIG. 6 is a perspective view of the outside of the box corner after complete engagement; and

FIG. 7 is a perspective view of the inside of the box corner construction of FIG. 6.

In the following description and in'the claims various details will be identified by specific names for convenience. The names however are intended to be generic in their application. Corresponding reference characters refer to corresponding parts in the several figures of the drawings.

The drawings accompanying, and forming part of, this specification disclose certain specific details of construction for the purpose of explanation of broader aspects of the invention, but it should be understood that structural details may be modified in various respects Without departure from the principles of the invention and that the invention may be incorporated in other structural forms than shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The blank A of FIG. 1 consists of suitable foldable sheet material, such as paperboard, and comprises terminal panels 11 and 12 articulated to further panels 13 and 14 along fold lines 15 and 16. The panels 13 and 14 are shown to be articulated to portions 17 and 18 of still other panels along fold lines 19 and 20, the central portion of the blank being omitted, as its details are not needed for an explanation of the invention.

Suffice it to say that the one terminal panel 11 has a tongue 21 formed thereon which protrudes beyond terminal edge portions 22 of the panel. The edge 23 of the tongue and the edge portions 22 constitute the terminal edge of that portion of the blank.

An aperture 24 is formed in the other terminal panel 12 and is elongated with respect to the transverse dimension of the blank, the latter being indicated by the arrow line 25. The tongue 21 is insertab'le into this aperture after appropriate folding of the blank at the several fold lines.

The aperture 24 is bordered by an engagement edge 26 on that side of the aperture which is nearest the terminal edge 27 of the panel 12 and is bordered by a bent tab edge 28 on the opposite side. The edge 28 borders an internal tab 29 which extends into the aperture in the direction towards the engagement edge 26.

An optional fold line 30 may extend to either side of the aperture 24 approximately in line with the base of the tab 29.

Turning back to the terminal panel 11, an internally disposed slit 31 is formed therein forming a curved locking tab 32 pointing in a direction opposite to the tongue 21 with respect to which the tab is approximately centered. The tab 32 is preferably centrally slit at 33.

The edge 31 of the locking tab is located within the body proper of the panel 11 exclusive of its tongue 21 and is placed sufficiently far inwardly within the body of panel 11, spaced from the edge 22, to coincide with, or cross, the engagement edge 26 at either side of the tip of the tab 32 in the position in which the tongue 21 is fully inserted in the aperture, as it is shown in FIG. 2.

In the structure A as shown in FIG. 2, the tongue 21 is inserted in the aperture 24 to underlie the panel 12. The locking tab 32, which is shown without cross hatching as it is centrally split, is bowed centrally by the internal tab 29 bearing down upon it. Laterally, however, it is raised by contact with lateral edges 34, 35 (see FIG. 1) which converge towards the engagement edge 26. The edges 34, 35 press against the underside of the lateral portion of the locking tab 32, thus assisting in the bowing of the board. The tip of the locking tab 32 still overlies the engagement edge.

By application of a force against the locking tab 32 within the area of the aperture 24, the tip of the tab 32 is snapped past the engagement edge into a position underlying the terminal portion of the panel 12. The resulting structure A" is shown in FIG. 3. The bowing of the locking tab and its depression mainly into the space provided by the aperture 24 is apparent from the illustration.

FIG. 4 illustrates a modified form of the internal slit 131 which is laterally extended to include straight portions 136. The resulting tab 132 is centrally split at 133 and lies within the panel 11, but outside the confines of the tongue 21 which protrudes beyond the terminal edge 22 of the panel 11.

The portion of the blank B shown in FIG. forms a box corner, the wall panels of which are interlocked by means of the above described lock. A main panel 37, which may be a box top panel or a box bottom panel, has wall panels 38, 39 articulated to it along fold lines 40 and 41. A corner flap 42 is articulated to the wall panel 39 along a corner fold line.

In order to simplify the explanation, the lock elements are designated by reference numerals differing from the above described elements by 200. Thus, internal tab 229 corresponds to internal tab 29 of FIGS. 1 to 3, aperture 224 corresponds to aperture 24, and so forth. The terminal edge 222 and the tongue 221 are shown curved, but may equally well be made straight.

The corner is formed by folding panel 38 upright with respect to the main panel 37, folding wall panel 39 towards an upright position and simultaneously folding the corner flap 42 with respect to the panel 39 at 43 and inserting the tongue 221 into the aperture 224. Pressure is then exerted against the locking tab 232 to snap its tip past the edge 226.

The locked corner is shown in FIG. 6 as it appears from the outside and in FIG. 7 as viewed from the inside, the tip of the locking tab 232 being snapped past the engagement edge 226.

What is claimed is:

1. In a carton of foldable material comprising interconnected panels forming the walls of the carton, at least one pair of said panels being interconnected by a tongue on one of said two panels, the edge of said tongue projecting beyond the terminal edge of said one panel, the tongue being inserted into an aperture in the other panel, the improvement in which the aperture is bordered by two spaced edges extending substantially transversely to the insertion direction of the tongue, one of said edges defining an internal tab extending into the aperture and directed opposite to the insertion direction of the tongue, the opposite edge of the aperture being an engagement edge, and in which the one panel comprises an internal locking edge located within the one panel proper, exclusive of the tongue, said locking edge being curved to form a locking tab pointing in a direction opposite to said tongue, said locking edge being located sufficiently far inwardly of said terminal edge of the one panel as to cross twice the said engagement edge in the position of said panels in which the tongue is fully inserted in said aperture, in which position the locking tab may be snapped past the engagement edge from a position overlying one surface of said other panel into a position overlying the opposite surface of said other panel, in which position the material of the so-displaced locking tab is depressed substantially into the space provided by said aperture and substantially without a corresponding deflection of the other panel in the direction in which the locking tab is displaced.

2. A carton construction according to claim 1 in which, in addition, said internal locking edge is curved so as to extend substantially parallel to the edge of said internal tab, and in which the engagement edge is straight.

3. A carton construction according to claim 1 in which said one edge which defines said tab comprises two straight terminal shoulder portions, one on each end of the curved centrally disposed curved portion, the length from one end of one shoulder portion to the opposite end of the other shoulder portion being at least as great as the length of said engagement edge.

4. A carton construction according to claim 1 in which said aperture comprises two lateral edges extending from the ends of said internal tab, said lateral edges being slanted to converge toward said engagement edge.

References Cited UNITED STATES PATENTS 432,475 7/1890 Brown 229-35 2,605,955 8/1952 Meller 22935 2,990,997 7/1961 Weiss 22940 3,112,854 12/1963 Persson 229-35 DAVID M. -BOCKENEK, Primary Examiner. 

